Percussion cylinder



July 15, 1952 v. c. STERRETT 2,603,191

PERCUSSION CYLINDER Filed Nov. 29, 1946 2 SHEETS-SHEET 1 IN V EN TOR. IM/VCE' C'. STERRETT Jy l5, 1952 v. c. STERRETT 2,503,191

PERCUSSION CYLINDER Filed Nov. 29, 194e ,2 SHEETS- swam 2 vl INVENToR.

4g VHA/CE d STERRE TT Patented .uy 15, i952 UNITED STATES PATENT OFFICE?. f f- Vance C. Sterrett, Logansport, Ind.Y Application November 29, 1946,'semaine('113,163y

iolaims. (01.12140) Y This invention relates to a percussion cylin.

der and it is one object of the invention to Drovide such a cylinder with locking mechanism which confines a quantity of compressed'air back of a piston assembly and which, by manual control or otherwise, is releasable at the will of the operator, and allows sudden freedom of a suiicient quantity of compressed air to act upon the piston assembly and cause the same to be shifted outwardly or forwardly at high speed away from the compressed air chamber.

Another object of the invention is to provide a percussion cylinder wherein a piston rod is rigidly attached to the piston assembly and moved with the piston assembly and thus given the same sudden impulse of velocity as the piston assembly during operation of the device, the entire mass thus taking on dynamic energyv in accordance with the physical law of mass times velocity.V

Another object of the invention is to provide a percussion cylinder wherein therpiston rod projectsoutwardly from the front end of the cylinder for delivering a powerful blow upon an:

object. the piston rod being also adapted to have a tool applied thereto and project from the front end of the piston rod imposition for use. Therefore the device will be very useful as a tool for piercing or punching holes in metal, upsetting rivets or metal rods, driving nails, tacks or brads, Where products are manufactured yin quantity production or as a pneumatic hammer carrying a drill for cutting concrete or similar work.

Another object of the invention is to provide a tool of this character wherein retracting mech-` anism is of such construction that the whole movingl mechanism retracts automatically to a reset position after each forward movement and may be immediately driven forwardly for an.- other striking movement.

Another object of the invention is to provide a percussion cylinder having ports and vents and valves so arranged that when the device is in use the piston will be automatically reciprocated at a rapid rate of speed.

The invention is illustrated in the accompanying drawings wherein: Y

Flgpl is a sectional view taken longitudinally through a percussion cylinder of the improved constructionV showing the piston rod in its retracted position. l Y

Fig. 2 is a view looking at the front end of the percussion cylinder.

Fig. 3 is a transverse sectional view taken along the'line 3--3 of Figure 1; 1

Fig; 4 is asecti'onal/view taken alongthe line -dofFigure 1. v Fig. 5 is a view partially in elevation andlpar.- tially -in-longitudinal section showing the piston.; rod in its extended position. l Y l Fig. 6 -is va fragmentary view takenr along .the line 6`6 of Figure 5. A f Y v kFig. A7 is a sectional view taken along the line I'I of- Figure 5. I i f 1 Fig. 8 is a vfragmentary view shoWing'the 'rear end'of a valve rod in elevation and adjoining portions in section. :j i. Fig'. 9 is a view showing-the piston vrod in longitudinal section. y i Y A f .I5

Fig. 10 is a sideelevation of the piston rod' head.l

Fig. 11 is a -view showing the valve-shift rod .inl elevation, a portion beingin section. Fig. 12 is aj'fragmentary sectional-view ofA a. modified form yof piston. Y i 1;

This percussion cylinder has a cylindrical Acas-- ing I formed of strong metal and having its front end` portion internally. threaded and screwed int'c engagement with therear end. portion of a'hous-- ing head 2 which isformed'with-acircumferenai tially extending shoulder'3 against which the cas= ing abuts. 'I'he housing head 2 projects vfor wardly from the casing and at its frontend. isl form-ed with an opening having its rear portion enlarged to form an annular seatV 5to receive the outstanding flange or shoulder 6 kof a ringl, which Hts-snugly in the opening and constitutes j an annular abutment for engagement bythe balls v8.-v These balls surroundr the elongatedpiston-'rod head -9 of a piston rodl IIJ which-has its f forward'portion of reduced diameter in order to form a 'bevelled shoulder IIL` A sleeve I 2x1-lts.y snuglyabout Vthe piston rod IB and atitsfronti end is counterbored to' form a forwardly project-3. ing annular flange I3 of such internal diameter..` that when the piston rcd and its head are in the retracted position shown in Figure 1 the lip Vwill fit about thefballsV and hold them snugly` about the reduced forward portion of the piston rod head 9 wherer they. Will be engaged by the sloping shoulder II and prevent outward `movement of.: the piston rod I0 and its head to an extended; position. When the sleeve I2 is` shifted rear-v wardly to the position shown in Figurel 5 the balls may be moved radially away from the piston rody head 9 by cam action .of the shoulder I I into the annulargroove I4 formed in the housing-head 2 and the piston rod head 9 may then move forwardly to the extended position shown in Figure' 5. A collar Its about the housing head 2l and` aeaiei 3 is formed with threaded openings I6 to receive threaded studs I1 which have stems I8 that project inwardly through slots I9 formed in the housing head 2 and fit into an annular groove 20, formed about the sleeve I2. When the sleeve is shifted rearwardly by pressure applied to the studs I1 the balls will be freed from the flange I3 and the piston rod head 9 and the piston may have reciprocating movement longitudinally in the casing and the head 2. A bore 2| extends longitudinally through the piston rod head 9 axially thereof for its entire length and constitutes a passage through which air may escapeA when the discs or blocks are screwed tightly upon the shank of the piston rod. Instead of forming the piston as set forth above it may be formed as shown in Figure 12. This piston 24a is of an annular one-piece formation and about its rear portion is formed a circumferentially extending seat 24h to receive the cup 21a which is channel-shaped in cross section and held in place by the bead 24e. The extreme rear portion of the piston rod I is of additionally reduced diameter and forms a sleeve 28 which projects rearwardly from the shank 23 of the piston rod. Anannular flange 29 defining a reduced opening 30. as shown in Figure 9, is formed within the piston rod and rearwardly of this flange, the piston rod is formed with radially extending ports 3| formed at, a forward incline so that they communicate with the portion of the casing forwardly o f the piston when the piston is in the position shown in Figure 1 and communicate with the interval cavity of the housing head when the piston is in the position shown in Figure 5. A helical spring 32 fits about the piston rod with one end abutting the sleeve I2 and its other end bearing against the piston and urging the piston and the piston rod I0 and piston rod head 9 rearwardlyin opposition to action of air in the casing rearwardly of the piston. When the piston is shifted for- Wardly by air pressure Athe spring is pressed forwardly into the rear portion of the housing head 2, as shown in Figure 5, and upon release of air pressure back of the piston the spring shifts the piston rearwardly and moves the piston rod and its head toward the retracted position of Figure 1.

The rear end portion ofthe casing is internally threaded to receive a hollow rear head 33 which has its forward portion internally thickened. as shown at 34 so that the sleeve 35 which extends longitudinally through the, rear head 33 will be spaced from the walls of the head for the major portion of its length andthus provide'a passage 36 from which lead ports 31. A cap 38 is screwed upon the threaded rear portion of shank 39-01 the rear head33 and has its internally bevelled front end tightly engaging the bevelled rear surface of the annular flange 40 formed about lthe rear head 33, and integral therewith and engaged by the rear en d of the casing I-. rounded at its inner end by a collar 42 is formed A threaded opening 4I sur-1 through the center of the cap 38 so that a pipe or hose leading from a supply of air under pressure may be connected with the implement and about this collar 42 engages the rear end of a helical spring 43 which has its front end portion engaged about a cap 44 so that the cap will be urged forwardly and the bevelled front face of its flange 45 forced into the rear end of the sleeve 35 where it has wedging t and forms a tight closure for the rear end of the sleeve. Air entering the chamber 46 dened by the cap 3S flows forwardly through the passage 35 and through the ports 31 and the forward portion of the sleeve 35 into the cylinder of the casing I rearwardly of the piston and acts upon the piston to force the piston forwardly and move the piston rod I0 and its head 9 forwardly to the extended position of Figure 5 when the sleeve I2 is shifted rearwardly and the balls allowed to move radially of the piston rod head 9 to the releasing position.

A valve-shift rod 41 which has an externally thickened forward portion 48 extends longitudinally through the piston rod I5 and the sleeve 35 in axial relation thereto and through the rod 41 is formed a longitudinally extending bore or passage 49. A flange 5Il surrounds the front end of the shift rod so that the enlarged forward portion thereof will be spaced from walls of the piston rod and provide a'passage 5I which communicates with the rear portion of the casing by way of ports 52 formed through the sleeve 28. When the piston rod and its head are in the retracted position shown in Figure l the ports 52 are blocked or closed by a sleeve valve 53 which ts slidably about the shift rod and engages theshoulder 54 shown in Figure 11 at the rear end of the forward portion 48 of the shift rod 41. When the collar I5 is shifted rearwardly and the piston rod head allowed to move forwardly the flange 29 engages the flange 50 and the rod is shifted forwardly rbut during forward movement ofthe piston rod relative to the shift rod the ports 52 move to a position forwardly of the valve sleeve, as shown in Figure 5, andy air may then flow through the ports `52 and the passage 5I and from passage 5I through the ports 3l into the portion of the casing in front of the piston. A gasket 55 fits into a pocket-like recess 56 formed in the front face of the cap 44 and when the shift rod 41 is moved rearwardly to the position shown in Figure 1 a` nut 51` screwed upon the threaded rear end of the shift rod engages the gasket and forms a seal about the rear end cf the shift rod, and as the A the nut 51 and prevent, damage bybiows delivered rear end of the passage 49 is now sealed instead of being unobstructed as shown in Figure 5 the gasket prevents flow of air through the passage 49 of the shift rod into the chamber 58 of the pistonrod` from which air flows through the passage 2I of the piston rod head. A valve 59V of piston-like formation is carried by the shift rod 41 for controlling flow of air through the port 31 and has end members or disks 60 and 6I engaged by cups 62 and 63 which are clamped against ends of a, sleeve or spacer G4 by the outwardly ilaredends 65 of a tubular core 66 which passes through the "valve elements of the valve and hold them in close fitting compact engagement with each other. Referringto Figure 8 it will be seen that a shock-absorbing washer 61 and steel thrust washers 68 t about the shift rod 41 between the' spool valve- 59..,and

during operation of the device.

so that the piston 24 will be subjected to air pressure. The air pressure is such that vwhen the collar I isv shifted rearwardly and the sleeve I2' shifted rearwardly the piston rod I9 will. be moved forwardly and cause the piston redhead 9 to be moved forwardly to the extendedposition of Figure 5. As the piston rod moves forwardly the ports 52 move to a position inyfront of the sleeve 53 so that air in the rear portion ofthe casing may flow through the vports 52 andthe passage 5I and through the ports 3l into the forward portion of the casing and the flange 29 then engages the flange 50 and causes the shift rod 41 to be carried forwardly with the piston rod and move the valve 59 forwardly into blocking relation to the ports 31. The spring 32 is compressed during forward movement of the piston rod and when the ports 31 are blocked the spring lwill expand and shift the piston rod rearwardly and spent air in the rear portion of the casing will flow into the front portion of the casing and out through the exhaust port 69 to the atmosphere. During rearward movement of the piston rod the shift rod 41 at yfirst remains stationary but when the rear endgofthe piston rod engages the valve 59 this valve and the shift rod will be carried rearwardly until the valve is out of blocking relation to the ports 31 and air under pressure may again enter the rear portion of the casing and act upon the piston and shift the piston rod forwardly while the shift rod remains in the position shown in Figure 1 with its rear end abutting the cap 44. The parts will then again be in the position shown in Figure 1 and air under pressure will again act upon the piston and move the piston rod and its head forwardly to the extended position. This reciprocating movement of the piston rod and its head will continue at a rapid rate of speed as long as the collar I5 is in the rearwardly moved position, but when the collar I5 is returned to the position shown in Figure 1 operation of the tool will cease as the balls 8 will then preventforward movement of the piston rod and its head. Air in the rear portion of the sleeve 35 may flow freely through the passage 49, chamber 58. and the passage 2| and discharge into the atmosphere as long as the rear end of the thrust rod 41 is out of engagement with the cap 44. Therefore formation of an air cushion in the rear portion of the sleeve will be prevented and rearward movement of the thrust rod 41 and the spool valve 59 will not be interfered with. The fact that the rear end of the sleeve 35 is closed by a spring-pressed cap permits the elements to be easily assembled and also assures a right closure of the rear end of the passage 49 when the thrust rod is in the position shown in Figure 1.

Having thus described the invention. what is claimed is:

1. A pneumatic tool comprising a cylindrical casing, heads at front and rear ends of said casing, a sleeve in the front head having its bore disposed axially of the casing and the heads, a cap carried by the rear head and defining an air chamber having an inlet at its outer end for air under pressure. a piston rod shiftable longitudinally 'in the'casing and thesleeveand having its forward portion projecting outwardly ,from the front head, means releasably holdingthe piston rod in a retractedl position. a piston about the piston rod, a spring about the piston rod between the sleeve and the piston urging the piston rod and the piston rearwardly, said piston rod having a longitudinal bore and being formedwith side" portscommunicating with the Acasing in front of Vthe piston and with other .ports com-.- municating with thecasing back of the piston. the front head. having van outlet port. a sleeve in the rear head having its walls spaced therefrom for a vportion of its length and together therewith forming an V"airpassage leading for` wardly from the air chamber in the cap,there being ports formed through the sleeve' and con necting withthe front end of the air passage. a tubular shift rod extending llongitudinally through said sleevein the rear head and into the rear portion of the piston rod and having ak lost motion connection with the piston rod. a valve carried by the shift rod and moved out of blocking relation to the ports of the piston rod back tothe piston when the piston rod is shifted forwardly independent of the shift rocha Valve carried by the shift lrod within the sleeve and moved therewithinto blocking relation to the ports of the sleeve when the shift rod is moved forwardly. and a closure for the rearend of the sleeve having closing engagement with the rear end of the shift rod when the shiftl rod is in a rearwardly moved position. u Y

2. A pneumatic tool comprising a cylindrical casing having front and rear heads, an air chamber back of the rear head having an air inlet, a member in the front head having a bore extending longitudinally of the casing, a tubular piston rod shif'table longitudinally in the casing and through the bore of the member in the front head, means for releasably securing the piston rod retracted, a piston carried by said piston rod and disposed in the casing Ibetween the front and rear heads. the piston rod being formed with a longitudinal bore and with side ports in front of and in back of the piston, a spring urging the piston and the piston rod rearwardly. a. sleeve in the rear head having its ends communicating with the air chamber and the rear end of said casing, there being space about the sleeve forming an annular air passage leading from said air chamber about the sleeve and communicating with the side ports formed through the front end portion of said sleeve. the front head being formed with an air exhaust port, a shift rod extending longitudinally through the sleeve and into the rear portion of the bore of the piston rod and carrying a front valve normally in 4blocking relation to the ports of the piston rod back of the piston and a rear valve normally out of blocking relation to the ports in the front end portion of the sleeve, the piston rod having a lost motion connection with the shift rod and when shifted forwardly first moving its ports out of blocking relation to the front valve ofl the shift rod and then having engagement with the shift rod to carry the shift rod forwardly with the piston rod and move the rear valve of the shift rod into blocking relation to ports of the sleeve.

3. A pneumatic. tool comprising a cylindrical casing having front and rear heads and an air chamber yback of the rear head having an air inlet, a member in the front head formed with a bore extending longitudinally of the casing, a

- ofthe piston and near its front end heing'formed withside ports. connecting, with the annular air passage, the.A frontVheadrbeing formed with ariexhaust, portand. the piston; rod being formed with sidei portsv locatedA front, -of Yand back; of the-,piston and, allowing now no fga-ir forwardly through the tubuar;pistonV rodgpast the pistonduring rearward movement ofthe piston, a shift rod movable longitudinallyhrough thesleeve and tlietubular pistonl rod and carrying front and rear valves for controlling "flow of air through the side ports of the sleeve and the rear ports of the pistonrod, and a lostv motion connection between the piston rod and thelshift rod whereby the piston rodmay have longitudinal movement relative to the shift rod vfor a portion of itsmovement and eiect movementiof its rear ports into and out of blocking relation to the front valve of the shift rod and then carry the shift rod longitudinally with it and move therear valve of` the shift rod out of blocking relation to the side ports ofthe sleeve in the rear Ahead.

4. A pneumatic tool comprising a cylindrical casing, an air chamber. at the rear end of said casing having an air inlet, a headv at the front end ofvsaid casing formed` with an exhaust port and provided withzaJ bore, the. rear head having an air inlet port, a tubular piston rod shiftable longitudinally, through the casing and the bore of the head ironia retracted position to an extended position, apiston carried by saidpiston rod within the casing and. movingwith the piston rod longitudinally in thecasing, a spring urging the piston and therpiston rod rearwardly,there being anairpassage extending forwardly from the air chamber" and communicating with the casing backl oft-he piston, the tubular piston rod being formed with side portsin front'of and back of the piston and establishingl communication through the piston rod between portions of the casing back offand in front of the pistona shift rod slidable longitudinally: by action of the piston rod, and valves for controlling'flow ofzair through the rear ports-,in the piston rod andlthrough the air passage carried by the shift rod and moved to adjusted positions by movement of the piston rod when the actuating rod isvmoved longitudinally during movementof the piston rod.

VANCE c. s'rEaRE'rr.

REFERENCES CITED- y The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,264,318 McGrath Apr. 30, 1918 2,100,092 Tear Nov. 23, 1937 2,158,568 Borrn May 16, 1939 

